Timing switch mechanism with manual adjustable cam

ABSTRACT

The mechanism is arranged in a clock driven either by a main spring or a battery, and comprises a manually rotatable switch cam, of insulating material, having three stepped portions of progressively increasing height on its periphery and three pits or dents in its periphery, each related to one of the stepped portions. The timing switch includes two relatively fixed contact springs and a third intermediate and movable contact spring, each of the relatively fixed springs having a contact thereon engagable with a respective contact on the intermediate spring. A spring engagable in the notches releasably retains the switch cam in a selected operated position. A flexible contact arm connected to one of the two relatively fixed contacts engages an annular contact on an unlocking wheel, and a projecting contact finger is secured to an hour wheel of the clock. The annular contact has a radially inwardly projecting extension which is engagable by the contact finger on the hour wheel. The intermediate contact is normally engaged with that fixed contact which is not connected to the contact arm engaging the annular or ring contact. In another embodiment the intermediate contact and one of the fixed contacts are extended for cooperation with another cam forming part of a mechanism whereby a transistor radio, when turned on, may be automatically turned off by the clock after a preset time interval.

United States Patent [1 1 Kudoh et al.

[S4] TIMING SWITCH MECHANISM WITH MANUAL ADJUSTABLE CAM Inventors: Tetsuo Kudoh, Kitakatsushika-gun; Hideo Koide, Urawa-shi, both of Japan Rythm Watch Company, Limited, Tokyo, Japan Filed: Feb. 29, 1972 Appl. No.: 230,345

[73] Assignee:

[30] Foreign Application Priority Data Mar. 4, 1971 Dec. 16, 1971 Japan ..46/l3292 Japan ..46/l17953 US. Cl. ..200/38 R, 200/33 B, 200/37 A IntQCl. ..H0lh 43/10, HOlh 7/08 Field of Search ..200/38, ll G, 33 R,

200/33 B, 35 R, 37 A;307/14 l.4, 141.8

References Cited UNITED STATES PATENTS James, Jr. ..200/38 FB Lynch et al ..200/1 1 G Robinson et a1. ....200/38 R X Boyles ..200/38 F13 X I Assmus et a1. ..200/38 FB X Primary ExaminerJ. R. Scott Attorney-John J. McGlew and Alfred E. Page June 5, 1973 571 I ABSTRACT The mechanism is arranged in a clock driven either by a main spring or a battery, and comprisesa manually rotatable switch cam, of insulating material, having three stepped portions of progressively increasing height on its periphery and three pits or dents in its periphery, each related to one of the stepped'portions. The timing switch includes two relatively fixed contact springs and a third intermediate and movable contact spring, each of the relatively fixed springs having a contact thereon engagable with a respective contact on the intermediate spring. A spring engagable in the notches releasably retains the switch cam in a selected operated position. A flexible contact arm connected to one of the two relatively fixed contacts engages an annular contact on an unlocking wheel, and a projecting contact finger is secured to an hour wheel of the clock. The annular contact has a radiallyinwardly projecting extension which is engagable by the contact finger on the hour wheel. The intermediate contact is normally engaged with that ,fixed contact which is not connected to the contact arm engaging the annular or ring contact. In another embodiment the intermediate contact and one of the fixed'contacts are extended for cooperation with another cam forming part .of a mechanism whereby a transistor radio, when turned on, may be automatically turned off by the clock after a preset time interval.

8 Claims, 9 Drawing Figures INSULATION PAIENTEBJUN Sim 3737. 598

SHEET 1 BF 3 INSULATION PATENTEUJUH 5 m5 Q suma'um FIGA FIG. 3.

FIG.5

PATENTED JUN 5 I973 SHEET 3 0F 3 TIMING SWITCH MECHANISM WITH MANUAL ADJUSTABLE CAM BACKGROUND OF THE INVENTION The present invention relates to a timing switch mechanism for a transistor radio, and more particularly to a timing switch mechanism where the individual operations of making or breaking of the circuit of the transistor radio after a predetermined time interval as well as the operations of instant making or breaking of the circuit, can be performed using fewer Operating Shafts.

There have hitherto been known the mainspring driven typeand battery driven type-clocks with a timing switch for a transistor radio arranged therewith, where the circuit of the radio is automatically made upon the lapse of a predetermined time interval so that the radio performs the function of an alarm clock. However, in these clocks there have been used at least two switches, i.e., one for the timing operation and the other for the instant making or breaking of the circuit these clocks have had disadvantages in that constructions become complicated and expensive.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a timing switch mechanism to be arranged in the mainspring driven typeor battery driven typeclock, where the individual operations concerning a transistor radio may be performed by means of using one operating shaft, or with an auxiliary operating shaft together with such one operating shaft.

An object of the present invention is to provide a timing switch mechanism to be arranged in the mainspring driven typeor battery driven type-clock, where making or breaking of the circuit of the transistor radio after a predetermined time interval as well as instant making and breaking of the circuit canbe performed by means of rotary operation of fewer operating shafts.

Another object of the invention is to provide a timing switch mechanism to be arranged in the mainspring driven typeor battery driven type-clock, where the individual actuations of the transistor radio can be performed by means of a simplified construction as a whole.

A further object of the invention is to provide a timing switchmechanism to be arranged in the mainspring driven typeor battery driven type-clock, wherethe actuations of the transistor radio can be performed by means of simple operations corresponding to fewer operating shafts.

Still further objects of the invention will hereafter be understood from the explanation with respect to the embodiments of the invention in reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmental plan view of an embodiment of the present invention showing the state where the LII timing switch has been set to make the circuit of the radio after a predetermined time interval and thereafter the circuit is made at such time.

FIG. 2 is an explanatory fragmental side view of the same embodiment with that in FIG. 1.

FIG. 3 is an electric circuit diagram of the same embodiment of the invention in which the mechanism is in the state in FIG. 1. a

FIG. 4 is an electric circuit diagram of the same embodiment of the invention in the state where the circuit of the radio is instantly broken from the state in FIG.

- FIG. 5 is an electric circuit diagram of the same e'rnbodiment of the invention in the state where the circuit of the radio is instantly made at a voluntary time.

FIG. 6 is a fragmental plan view of another embodiment of the invention showing the state where the timing switch has been set to make the circuit of the radio after a predetermined time interval and thereafter the circuit is made at such time, with its left part being illustrated in an electric circuit diagram style as the construction of such left part is identical with the embodiment in FIG. 1.

FIG. 7 is an explanatory fragmental side view of the same embodiment with that in FIG. 6, with the flexible contact plate and the lower contact plate being omitted.

FIG. 8 is a-fragmental plan view of the same embodiment with that in FIG. 6, showing the state where the timing switch is set to make the circuit of the radio instantly but to break such circuit after a preselected time interval, its left part being illustrated in an electric circuit diagram style.

FIG. 9 is a fragmental left side view of the embodiment of the invention shown in FIG. .1.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1, the switch cam 1 is secured to the operating shaft 2 which is rotatably mounted in the dial base 3 made of insulating material to be rotated manually, and three-step portions, including lower portion 1a, middle portion 1b and higher portion 10, are formed in adjacency on the peripheral surface of cam 1. In addition, three pits or notches 1d, 1e and 1f are formed in order on the substantially diametrically opposite side of the peripheral surface of cam 1. In the vicinity of switch cam 1, three contact plates, that is, an upper contact plate 4 having a contact 4a at its free end, a flexible intermediate contact plate 5 having two contacts 5a, 5b on its upper and lower surfaces, respectively, near its free end, and a lower contact plate 6 having a contact 6a at its free end, are secured in adjacency to dial base 3, in order, through their other ends,

with screws 4b, 50, 6b, respectively. The free end 5d of the flexible contact plate 5 is disposed so that, upon rotation of cam 1, this free end 51; solely faces lower portion 1a of the cam 1 without contacting with the latter, and it comes in light contact with middle portion 1b of the cam 1, and further it comes in strong contact with higher portion 1c of the cam l to be pressed by the latter. That is, when the free end 5a of the flexible contact plate 5 faces the lower portion 1a of the cam 1, contact plate 5 springs upward and its contact 5a comes in contact with the contact 4a of contact plate 4 (as shown in FIG. 1). When the free end 5d comes in strong contact with the higher portion 10 of the cam 1 to be pressed,

the contact b comes in contact with the contact 6a of contact plate 6 (as shown in FIG. 5). When the end 5d comes in slight contact with the middle portion lb cam 1, neither of the contact 5a or 5b comes in contact with contact 4a and 6a (as shown in FIG. 4).

A pressing spring 7 is secured to the dial base 3 through its one end, and its other end 7a is adapted to press the peripheral surface of said switch cam 1 continuously, whereby free rotation of cam 1 is prevented. When end 7a of the pressing spring 7 engages the upper pit 1d of the cam 1, the lower portion la of cam 1 faces the end 5d of the flexible contact plate 5, and when end 7a engages the middle pit 1e or lower pit l f, the middle portion lb or higher portion of the cam 1 comes in contact with the end 5d of the flexiblecontact plate 5, respectively.

A flexible contacting arm 8 is secured with its one end to the dial base 3 by a screw 8a, and its forked other ends 8b, 8b continuously press against the ring contact 10a of a ring-shaped nonconductor plate 10 which is adhered rigidly on the unlocking wheel 9. That is, ring contact 10a is electrically insulated from unlocking wheel 9. A protrusion 10b is formed on the radially inner edge of ring contact 10a to indicate a predetermined time when the circuit of the radio will be selected to make. A projecting contact 11a is fixed on the lower surface of the hour wheel 11, which is rotatably mounted concentrically with unlocking wheel 9, and is arranged'in such a way as it comes in contact with protrusion 10b of the ring contact 10a, or disengages the latter as the rotation of the hour wheel 11 continues.

The upper contact plate 4 is electrically connected with the clock movement through the upper plate (or frame plate) 12, while the lower contact plate 6 is electrically connected with the contacting arm 8 (in the embodiment in FIG. 1 the basal end of the contact plate 6 and that of contacting arm 8 are constructed as a unit). The flexible contact plate 5 and the contact plate 6 are respectively connected with the radio through lead wires 13 and 14.

In the embodiment of the invention shown in FIG. 1-5, firstly, in order to make the circuit of the radio 15 after a predetermined time interval, the operating shaft 2 is rotated and the upper pit 1d of the switch cam 1 is caused to engage with the free end 7a of the pressing spring 7 to face the lower portion 1a of the cam 1 to the free end 5d of the flexible contact plate 5, and thereupon the alarm hand connected with the unlocking wheel 9 is caused to rotate was to point at the predetermined time-figures on the front dial. At this moment, the contact 4a comes in contact with the contact 5a (as in FIG. 1). However, the projecting contact 11a of the hour wheel 1 1 does not yet come in contact with the protrusion 10b of the ring contact 10a. Thereafter, upon lapse of the predetermined time interval, the projecting contact 11a comes in contact with protrusion 10b through the rotation of the hour wheel 11, as shown in FIG. 3, so that thecurrent flows in a circuit including radio 15 lead wire 14 contact plate 6 contacting arm 8 ring contact 10a projecting contact 11a hour wheel 11 contact plate 4 flexible contact plate 5 lead wire 13 radio 15, and the radio begins to operate.

In the same embodiment, in order to break the circuit of the radio 15 instantly from the-state when the circuit has generally been made, the switch cam 1 is rotated and the middle pit le of the cam 1 is caused to engage with the-free end 7a of the spring 7. At this moment, the free end 5d of the flexible contact plate 5 is lightly pressed by the middle portion lb of the cam 1, whereby both contacts 5a, 5b of the flexible contact plate 5 are released from the contacts 4a and 6a respectively, so that the circuit of the radio 15 is broken to stop operation of the radio instantly (as in FIG. 4).

Further, in the above embodiment, in order to make the circuit of the radio 15 at a voluntarily selected time, the lower pit 1f of the cam 1 is caused to engage with the end 7a of the spring 7. At this moment, the free end 5d of the flexible contact plate 5 is strongly pressedby the higher portion 1c of the cam, whereby the contact 5b comes in contact with the contact 6a of the lower contact plate 6, so that the current flows in a circuit including radio 15 lead wire 14 contact plate 6 flexible contact plate 5 lead wire 13 radio 15, and the radio begins to operate instantly.

In the above embodiment of the present invention, in case the timing switch has been set to make the circuit of the radio 15 upon the lapse of a predetermined time interval and thereafter the circuit is made at such predetermined time, the succeeding time interval of making of the circuit of the radio is the time interval of contacting between protrusion 10b of the ring contact 10a and projected contact 11a, and therefore such time interval is governed by the width of the protrusion 10b. In the case of FIG. 1, this time interval comes to about an hour. Y 2

In the present invention, a conventional alarm limiting mechanism of the alarm clock can be combined together with the above-described timing switch. For instance, a protruding portion 1g is formed between the upper pit 1d and the higher portion 10 of the periphery of the switch cam l, and the alarm bellcan be stopped or'rung by means of causing protruding portion lg to contact with a conventional alarm limiting lever 16 or to release therefrom. That is, as shown in 'FIG. 1, in case the free end 7a of the pressing spring 7 engages with the upper pit 1d of the switch cam 1, protruding portion 1g comes in contact with alarm limiting lever 16 to stop its action, through routine engagement of a projecting cam 11b of the hour wheel 11 with a dent cam 9a of the unlocking wheel 9 to drop the alarm switch lever 17 at the predetermined time, resulting in ringing of the alarm bell (refer to the state of FIG. 2). On the contrary, when the switch cam l is rotated as in' FIG. 4 or FIG. 5, the alarm limiting lever 16 is released from the protruding portion lg of the cam l and further pressed by a spring 18 located on the opposite side from protruding portion 1g, whereby alarm limiting lever 16 acts to stop the alarm bell. Spring 18 has a fixed end secured to dial base 3. That is, in such situations even if the alarm switch lever 17 is put into its dropped state, the alarm bell can not be rung.

In the above embodiment of the invention, the protruding portion lg on the peripheral surface of the switch cam l is not necessarily limited to being located at the region between the pit 1d and the higher portion 1c of the cam l, but it is possible to locate the protrusion at another region of the peripheral surface of the switch cam l.

FIG. 6 shows another embodiment of the present invention, but the left part of this FIG. 6, that is, the constructions of the switch cam l, the contact plates 4, 5, 6, the pressing spring 7, the contacting arm 8, the nonbase 3 near the upper side of the right'end (the back side of the contact 5e) of the flexible contact plate 5.

To this operating shaft 19, a friction plate 20, consisting of two thin metallic plates compressed to adhere closely to each other, and a sleep cam 21, made of insulating'material, are rigidly secured. A protruding sector or'arc d-20bhaving a central angle of about 90, is formed on the periphery of friction plate 20, sector 20a-20b being adapted, when the second operating shaft 19 is manually rotated through some rotary angle, to nip resiliently or to release the circumferential part of a friction wheel 22 which is connected with the clock perform such an operation, the pit 1e of the switch cam movement, whereby friction plate 20 is thereafter caused to rotate together with friction wheel 22, or remain as it stopped. A dent 21a and a projecting finger 21b are formedin adjacency on the periphery of the sleep cam 21, and the rotary angle of cam 21 is limited to'about 90 which is the angular size of the sector 20a-20b of friction plate 20, through engagement of finger 21b with stoppers 23 and 23'. The dent 21a is so arranged as it does not overlap upon the sector 20a-20b in the plan view of FIG. 6.

. The right end 5f of the flexible contact plate 5 is adapted to come resiliently in contact with the ordinary circumferential surface of the sleep cam 21, whereby contact plate 5 is so pressed that its contact 5e comes in contact with the contact 6c' of the contact plate 6.

' But when the end sf of the flexible contact plate 5 engages in the dent 21a of cam 21, the contact Se is releasedfrom the contact 6C. At this moment, the finger 21b of the cam 21 engages stopper 23 and, on the other hand, the protruding sector 20a-20b of the friction plate, which is connected as a unit with cam 21, is released from the nipping engagement-with the friction wheel 22. The friction plate 20 is arranged in such a way that, when the sleep cam 21 is rotated counterclockwise manually and the end 5f of the flexible contactvplate 5 comes in compressive contact with the ordinary circumferential surface of the cam 21 from the abovementioned state (where the end 5f of the flexible contact plate 5 has engaged in the dent 21a of the .cam 21), sector 20a-20b of friction plate 20 begins to nip resiliently the circumferential part of friction wheel 22 from the left end 20a of sector 202120b. However, even when the cam 21 is further rotated so far that its projecting finger 21b engages the other stopper 23., sector 20a-20b of the friction plate 20 remains as it nips the circumferential partof the frictionwheel 22. Reference character 24 in FIG. 7 indicates the minute wheel.

In the embodiment of the invention as shown in FIGS. 6-8, operations of making the circuit of the radio after a predetermined time interval, of breaking the circuit instantly from the state where the circuit is made, of making the circuit instantly at a voluntary time, as well as the operations of repressing or allowing the action of the alarm limiting lever, are all identical with those explained with respect to the embodiment in FIG.

1 (but in these cases contacts 5e and 6c on the right l is, as shown in FIG. 8, engaged with the free end 7a of the pressing spring 7 to release the contacts 5a and 5b of the flexible contact plate 5 from the individual contacts 4a and 6c of the contact plates 4 and 6, respectively, and further the second operating shaft 19 is manually rotated counterclockwise through some rotary angle fromthe state where the right end 5f of the flexible contact plate 5 has engaged in the'dent 21a of cam 21, so as to let the end 5f of the flexible contact plate 5 comes in compressive contact with a predetermined point on the ordinary circumferential surface of the sleep cam 21. At this moment, current flows, as in FIG. 8, in a circuit including radio 15 lead wire 14 contact 6c contact 5e lead wire 13 radio circumferential part of the friction wheel 22. Thereby plate 20 begins to rotate clockwise in combination with the friction wheel 22. On the lapse of the predetermined time interval, the right end 5f of the flexible contact plate fall into the dent 21a of the sleep cam 21 and the contact Se is released from the contact 60, whereby the radio ceases to operate.

In the above-mentioned embodiment of the invention shown in FIG. 6-8, in case of setting the circuit of the radio to make instantly but to break such circuit automatically after a predetermined time interval, the longest adjustable time interval is governed by the length of the circumference and the rotation velocity of the friction wheel 22, as well as thelength and angular size of protruding sector 20a-20b of friction plate 20. The angular size of sector 20a-20b may be increased theoretically to approximately 360. In the above embodiment, such longest adjustable time interval is about 60 minutes. The second operating shaft 19 is so made that it can be rotated manually by a knob on its end extend ing through the front of the clock.

While specific embodiments of theinvention have been shown and described in detail to illustrate the application of the principles of the invention it will be understood that the invention may be embodied otherwise without departing from such principles.

What we claim is:

1. A timing switch mechanism, arranged in a clock driven by spring or battery power and having a dielectric dial base and a clock movement on'the dial base including an unlocking wheel and an hour wheel, said mechanism comprising, in combination, a manually operable switch cam secured to an operating shaft rotatably mounted in said dial base, and operable between an intermediate position and first and second end positions; respective step portions on the periphery of said switch cam corresponding to each of said positions thereof; three detent notches in the periphery of said said cam; a pressing spring having one end secured to i said dial base and a free end pressing the periphery of said switch cam to engage in said detent notches to re,- leasably retain said cam in an operated position; three contact plates, including first and second relatively fixed outer contact plates and a resilient intermediate contact plate, having inner ends secured to said dial one end .secured to said dial base and a free end engaged with said ring contact and electrically connected to said second outer contact plate; a projecting contact finger on said hour wheel engageable with said radial extension responsive to rotation of said hour wheel; and leads electrically connected to said resilient intermediate contact plate and to said second outer-contact plate for connection to the energizing circuit of a radio to be controlled by said timing switch mechanism; said cam step portions, in a first end position of said switch cam, being disengaged from the free end of said intermediate contact plate so that the latter maintains its position engaging a contact thereon with a facing contact on said first outer contact plate; said cam step portions, in the intermediate position of said switch cam, engaging the free end of said intermediate contact plate to maintain the latter disengaged from both outer contact plates; said cam step portions in the other end position of said switch cam engaging the free end of said intermediate contact plate and biasing said intermediate contact plate to engage a contact thereon with a facing contact on said second outer contact plate.

'2. A timing switch mechanism, as claimed in claim 1, in which said step portions comprise three circumferentially adjacent steps including a lower step, an intermediate step and a higher step; said lower step, in the first end position of said switch cam, being aligned with and out of engagement with the free end of said intermediate contact plate, said intermediate step, in the in- 'having an alarm limiting lever; spring means biasing said alarm limiting lever to a position maintaining said audible alarm inactive; and a protrusion on the periphery of said switch cam engageable with said alarm limiting lever in the first end position of said switch cam to deflect said alarm limiting lever to a position in which said audible alarm is effective.

- 4. A timing switch mechanism, as claimed in claim 1, in which said intermediate and second relatively fixed outer contact plates have respective extensions whose free ends carry facing normally disengaged contacts; a second manually operable operating shaft rotatably mounted in said dial base; a circular sleepcam fixed to rotate with said second shaft, and having anotch in its periphery; the extension of said resilient c'ontact'plate having a bent free end engaged with the periphery of said sleep cam, and engageable in said notch; saidlastnamed facing contacts being engaged when said bent free end is engaged with the periphery of said sleep cam and being disengaged when said bent free end engages in said last-named notch; said clock movement including a rotatable friction wheel; and friction means secured to said second shaft and selectively engageable with said friction wheel responsive toangulardisplacement of said sleep cam from an initial position, in which said bent free end is engaged in said sleep cam notch and said last-named facing contacts are disengaged to a position in which said bent free end is engaged with the periphery of said switch cam and said last-named facing contacts are disengaged; engagement of said friction means with said friction wheel effecting rota tion of said sleep cam in an angular direction to re engage said bent free end in said notch to disengage said last-named facing contacts after a predetermined time interval corresponding to the extent of angular displacement of said sleep cam from said'initial position.

5. A timing switch mechanism, as claimed in claim 4, in which said switch cam has a radially outwardly projecting finger; a first stop engageable'with said finger in said initial position of said sleep cam; and a second stop spaced angularly from said first stop and engageable with said finger to limit the angular displacement of said sleep cam away from its initial position.

6. A timing switch mechanism, as claimed in claim 5, in which said friction means comprises a friction plate consisting of two thin closely superposed metallic plates defining, a radially outwardly extending sector having a predetermined arcuate extent corresponding to the angular distance betweensaid first and second stops; the outer edges of the two thin plates at said protruding sector diverging slightly to provide for said protruding sector gripping the rim of said friction wheel upon displacement of said sleep cam from its initial position.

7. A timing mechanism, as claimed in claim- 6, in which said radially outwardly extending finger extends outwardly from the edge of said sleep cam notch leading in the direction of angular displacement of said sleep cam from its initial position.

' 8. A timing switch mechanism, as claimed in claim 7, in which said clock further includes an audible alarm having an alarm limiting lever; spring means biasing said alarm limiting lever to a position maintaining said audible alarm inactive; and a protrusion on the periphery of said switch cam engageable with said alarm limiting lever in the first end position of said switch cam to deflect said alarm limiting lever to a position in which said audible alarm is effective. 

1. A timing switch mechanism, arranged in a clock driven by spring or battery power and having a dielectric dial base and a clock movement on the dial base including an unlocking wheel and an hour wheel, said mechanism comprising, in combination, a manually operable switch cam secured to an operating shaft rotatably mounted in said dial base, and operable between an intermediate position and first and second end positions; respective step portions on the periphery of said switch cam corresponding to each of said positions thereof; three detent notches in the periphery of said cam each corresponding to an operative position of said cam; a pressing spring having one end secured to said dial base and a free end pressing the periphery of said switch cam to engage in said detent notches to releasably retain said cam in an operated position; three contact plates, including first and second relatively fixed outer contact plates and a resilient intermediate contact plate, having inner ends secured to said dial base and carrying contacts on their free ends; said first oUter contact plate being electrically connected to said clock movement and said intermediate contact plate being biased normally to engage a contact thereon with a facing contact on said first outer contact plate; the free end of said resilient contact plate being cooperable with said cam step portions; a ring contact adhered concentrically in electrically insulated relation to said unlocking wheel, and having a radial extension of a preselected angular extent; a flexible contact arm having one end secured to said dial base and a free end engaged with said ring contact and electrically connected to said second outer contact plate; a projecting contact finger on said hour wheel engageable with said radial extension responsive to rotation of said hour wheel; and leads electrically connected to said resilient intermediate contact plate and to said second outer contact plate for connection to the energizing circuit of a radio to be controlled by said timing switch mechanism; said cam step portions, in a first end position of said switch cam, being disengaged from the free end of said intermediate contact plate so that the latter maintains its position engaging a contact thereon with a facing contact on said first outer contact plate; said cam step portions, in the intermediate position of said switch cam, engaging the free end of said intermediate contact plate to maintain the latter disengaged from both outer contact plates; said cam step portions in the other end position of said switch cam engaging the free end of said intermediate contact plate and biasing said intermediate contact plate to engage a contact thereon with a facing contact on said second outer contact plate.
 2. A timing switch mechanism, as claimed in claim 1, in which said step portions comprise three circumferentially adjacent steps including a lower step, an intermediate step and a higher step; said lower step, in the first end position of said switch cam, being aligned with and out of engagement with the free end of said intermediate contact plate, said intermediate step, in the intermediate position of said switch cam, engaging and lightly pressing the free end of said intermediate contact plate to disengage its contact from the facing contact of said first outer contact plate, and said higher step, in the other end position of said switch cam, engaging the free end of said intermediate contact plate and deflecting the latter to engage a contact thereon with a facing contact on said second outer cam plate.
 3. A timing switch mechanism, as claimed in claim 5, in which said clock further includes an audible alarm having an alarm limiting lever; spring means biasing said alarm limiting lever to a position maintaining said audible alarm inactive; and a protrusion on the periphery of said switch cam engageable with said alarm limiting lever in the first end position of said switch cam to deflect said alarm limiting lever to a position in which said audible alarm is effective.
 4. A timing switch mechanism, as claimed in claim 1, in which said intermediate and second relatively fixed outer contact plates have respective extensions whose free ends carry facing normally disengaged contacts; a second manually operable operating shaft rotatably mounted in said dial base; a circular sleep cam fixed to rotate with said second shaft, and having a notch in its periphery; the extension of said resilient contact plate having a bent free end engaged with the periphery of said sleep cam, and engageable in said notch; said last-named facing contacts being engaged when said bent free end is engaged with the periphery of said sleep cam and being disengaged when said bent free end engages in said last-named notch; said clock movement including a rotatable friction wheel; and friction means secured to said second shaft and selectively engageable with said friction wheel responsive to angular displacement of said sleep cam from an initial position, in which said bent free end is engaged in said sleep cam notch and said last-nameD facing contacts are disengaged to a position in which said bent free end is engaged with the periphery of said switch cam and said last-named facing contacts are disengaged; engagement of said friction means with said friction wheel effecting rotation of said sleep cam in an angular direction to re-engage said bent free end in said notch to disengage said last-named facing contacts after a predetermined time interval corresponding to the extent of angular displacement of said sleep cam from said initial position.
 5. A timing switch mechanism, as claimed in claim 4, in which said switch cam has a radially outwardly projecting finger; a first stop engageable with said finger in said initial position of said sleep cam; and a second stop spaced angularly from said first stop and engageable with said finger to limit the angular displacement of said sleep cam away from its initial position.
 6. A timing switch mechanism, as claimed in claim 5, in which said friction means comprises a friction plate consisting of two thin closely superposed metallic plates defining a radially outwardly extending sector having a predetermined arcuate extent corresponding to the angular distance between said first and second stops; the outer edges of the two thin plates at said protruding sector diverging slightly to provide for said protruding sector gripping the rim of said friction wheel upon displacement of said sleep cam from its initial position.
 7. A timing mechanism, as claimed in claim 6, in which said radially outwardly extending finger extends outwardly from the edge of said sleep cam notch leading in the direction of angular displacement of said sleep cam from its initial position.
 8. A timing switch mechanism, as claimed in claim 7, in which said clock further includes an audible alarm having an alarm limiting lever; spring means biasing said alarm limiting lever to a position maintaining said audible alarm inactive; and a protrusion on the periphery of said switch cam engageable with said alarm limiting lever in the first end position of said switch cam to deflect said alarm limiting lever to a position in which said audible alarm is effective. 